50mpg from 1.4TDI90 on long trip - normal?

Hi.
I regularly get 60-65mpg on a long run out of my tdi75. Always leave climate on auto(pump always running anyway on an A2) and always use cruise control. Try using a product called cataclean. Have used the diesel version on my A2 and the petrol version on my daughters up. The car seems to want to rev now and a steady idle.
Best of luck
Steve
 
Filled up today £1.48 per litre ?.

Trip states exactly 50mpg.
My calculations were: 27 litres last fill up, shortly after fuel warning came on, 313 miles until fuel light came back. 27 litres = 5.94 gallons, so 52.69mpg. DIS seems pretty accurate.
I’ve put 7.90 gallons in this time, so to achieve 60mpg I need to get 474 miles before the fuel light returns. This will be difficult methinks.

Question though - I was nearly empty and I’ve filled the tank to second click, with less than 36 litres. Would there really have been 6 litres of fuel left in the tank and be that low on the dial?
 

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The warning is generally held to be at 7litres remaining in the tank. The tank sizes as given (34litres, 42litres) are somewhat nominal though. With my 34L one I can get very nearly all of that amount into it from 10-15 miles after the warning if I vent the tank after each click of the pump and add more, until it's completely full up to the neck. Similarly I remember getting 45litres into a 42L which I'd taken somewhat further after the warning.

The amount you have in the tank at e.g. the second click is going to vary depending on the slope forwards/backwards and side-to-side of the pump you fill up at, and also how fast you fill it. The most accurate MPG calculation is to brim it using the vent as above, drive it at least as far as the warning, then brim it with the vent again - and for good measure, at the same side of the same pump. By starting from completely full and returning to completely full, this takes out the inconstencies so you then know how much you've actually used over the intervening mileage.

The vent should only be used on TDIs though as petrol engines need the space for the fuel to vaporise into.
 
Proghound said:
The warning is generally held to be at 7litres remaining in the tank. The tank sizes as given (34litres, 42litres) are somewhat nominal though. With my 34L one I can get very nearly all of that amount into it from 10-15 miles after the warning if I vent the tank after each click of the pump and add more, until it's completely full up to the neck. Similarly I remember getting 45litres into a 42L which I'd taken somewhat further after the warning.

The amount you have in the tank at e.g. the second click is going to vary depending on the slope forwards/backwards and side-to-side of the pump you fill up at, and also how fast you fill it. The most accurate MPG calculation is to brim it using the vent as above, drive it at least as far as the warning, then brim it with the vent again - and for good measure, at the same side of the same pump. By starting from completely full and returning to completely full, this takes out the inconstencies so you then know how much you've actually used over the intervening mileage.

The vent should only be used on TDIs though as petrol engines need the space for the fuel to vaporise into.
Click to expand...

“Vent”? Sorry to be so dim but how do you vent as you fill? This sounds important!
 
@froggy
ONLY on diesel cars use this if you want to fill the tank completely.

Inside the filler neck you will find a little button. depress this and the top of the tank is vented allowing more fuel in. THIS SPACE IS CRITICAL FOR PETROL ENGINES TO ALLOW EXPANSION AND GASSING OF THE PETROL.
 
audifan said:
@froggy
ONLY on diesel cars use this if you want to fill the tank completely.

Inside the filler neck you will find a little button. depress this and the top of the tank is vented allowing more fuel in. THIS SPACE IS CRITICAL FOR PETROL ENGINES TO ALLOW EXPANSION AND GASSING OF THE PETROL.
Click to expand...
Im astonished!! I’ve driven approx. 110,000 miles in A2’s and never knew anything about a button in the filler neck!!
 
Got 70mpg on a 200 mile run today. 1.4tdi amf 75.
Vehicle is fully serviced and running sweet

I think it can do even better if it had CC and I slowed down a little...
FAB.
 
60mph on the cruise is the charm - plenty of torque for any hills or a quick burst up to 65 to pass the lorries a bit quicker. I got over 72mpg on the DIS in the 200-ish miles to Exeter last year, with three of us and luggage for a week in the car. It went down a few after I turned onto the A30 with all those steep hills though!
 
Around town is dropping me below 50, I did briefly hit 60mpg after a 20 mile run sticking to 55mph. Still need to change oil and all filters bar fuel filter and change wheels. After all that I’m confident I can hit 60mpg ??
 
Proghound said:
The warning is generally held to be at 7litres remaining in the tank. The tank sizes as given (34litres, 42litres) are somewhat nominal though. With my 34L one I can get very nearly all of that amount into it from 10-15 miles after the warning if I vent the tank after each click of the pump and add more, until it's completely full up to the neck. Similarly I remember getting 45litres into a 42L which I'd taken somewhat further after the warning.

The amount you have in the tank at e.g. the second click is going to vary depending on the slope forwards/backwards and side-to-side of the pump you fill up at, and also how fast you fill it. The most accurate MPG calculation is to brim it using the vent as above, drive it at least as far as the warning, then brim it with the vent again - and for good measure, at the same side of the same pump. By starting from completely full and returning to completely full, this takes out the inconstencies so you then know how much you've actually used over the intervening mileage.

The vent should only be used on TDIs though as petrol engines need the space for the fuel to vaporise into.
Click to expand...
Just be aware that fuel expands as it warns up, and fuel is usually, (not always), quite cool in it's underground storage, so will often get warmer once it's in your tank (depends on ambient obviously). So filling the tank to the absolute brim is unwise.
Mac.
 
PlasticMac said:
You do need to be careful with high pressures. If you over inflate the tyre, the contact patch is reduced, with only the centre of the tread on the road. This reduces grip, obviously, leads to uneven wear, and can cause overheating.
Take a careful look at the patch area.

OK higher pressure can save a smidgen of fuel, but weighed against not being able to stop, or losing control at speed, not worth the risk, imo.
Mac.
Click to expand...
I think the late Tony @A2cars warned of running higher tyre pressures on cars fitted with OpenSky (OSS); from memory he attributed damage to OSS resulting from the more jarring ride

Andrew
 
I have a tdi 90 and have have been getting around mid to late 40s mpg wise. It’s mainly used as an about town run around and serviced regularly. On the 17inch wheels and inflated to standard spec. I did a run from Manchester to Great Yarmouth and back last week and achieved 57mpg driving normally for me which is keeping to the speed limit. A roads all the way down. Mpg worked out on a uk mpg calculator online by miles done and litres used. ????
 
Aye it It was a good run, a628, m1, a57, a1, a17 and a47 cruise control mainly around 60. No traffic so no stopping and starting. Did a bit of pootling around town seeing some friends. It’s a fairly flat run most of the way. I was fairly impressed
 
So whats the optimun rev range to drive at in any gear?

I would have said as low as possible without labouring the engine which is the same as driving in the snow??
 
If you ask me, it's at peak torque, that way the engine can handle the variations of the road with a minimum of extra throttle. On a standard TDI75 the peak is 2200revs which equals 60mph - so 55-65mph is perfect. The figures on a 90 will probably be different - with a VNT turbo I expect a wider rev range where it produces over 90% of peak torque, on the 75 it's a bit of a spike around that 2200 mark.
 
Proghound said:
If you ask me, it's at peak torque, that way the engine can handle the variations of the road with a minimum of extra throttle. On a standard TDI75 the peak is 2200revs which equals 60mph - so 55-65mph is perfect. The figures on a 90 will probably be different - with a VNT turbo I expect a wider rev range where it produces over 90% of peak torque, on the 75 it's a bit of a spike around that 2200 mark.
Click to expand...

“2200rpm at 60mph” that’s good to know, my engine runs exactly at this, so after all its been through?? it’s doing well! I read earlier in the thread about tips on economy and found sticking behind a HGV (not too closely!) certainly made a difference ??
 
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